Unusual and surprising counters

本(ほん) is the counter for "long things" but it is also the counter for films. This is because films were long strips of film (stored in reels).

羽(わ) is the counter for birds, but it is also the official counter for rabbits (for which there are a few explanations). Although it is the official counter 匹(ひき) is also correct, and probably used more frequently.

足(そこ) counts things in pairs. 一足(いっそく) is one pair of shoes, or socks.